The central theme of this program is the role of retroviruses and retrovirus-related oncogenes in neoplastic change. The grant consists of seven individual projects which address the issue across a broad front. Project 1 is concerned with the location and function within the cell of tyrosine protein kinases encoded by a number of viral oncogenes and the molecules which serve as the substrates for these enzymes. Project 2 attempts to exploit the suppression of gene expression by anti-sense RNA to determine whether this strategy can be used to manipulate the expression of c-myc and c-ras oncogenes. Project 3 will explore the role of tyrosine protein kinases in the action of polypeptide hormones on differentiation and cell growth. Project 4 will involve purification and microinjection analysis of the protein of the myc oncogene. Project 5 concerns the chromatin structure of the myc oncogene and effects of retroviral integration events on myc chromatin structure and expression. Project 6 will examine the role of specific domains of the v-myc gene in the oncogenicity of avian myelocytomatosis virus. Project 7 will attempt to determine the role of two oncogenes, myc and Blym-1, in specific stages of virus induced lymphomagenesis in the bursa of Fabricius in chickens.